Forage Value Based on Nutrients

By Clif Little

A forage nutrient analysis is an underutilized tool. Nutrient content determines forage value. In addition, forage dry matter content influences livestock feed amounts required per day and ability to properly preserve forages for winter feeding. Consider the calculations values below for a second cutting grass hay (harvested in late June), a first cutting grass baleage (harvested in late May), and a first cutting perennial warm season grass hay (harvested in mid-July).

The value of the forage above was calculated by totaling the sum value of energy, protein, calcium, and phosphorus contained in each forage. The price per unit for each of these nutrients was obtained from the commodities below and calculated utilizing the University of Missouri-Columbia, Feedval III.

Feed prices utilized to calculate forage value were obtained locally 8/12/19. Prices for feed ingredients may vary significantly depending on the source. The calculations above place no value on forage moisture.

Livestock feed to meet their dry matter (DM) needs, as the nutrients they need to survive are contained in the dry material of the feed source. Have you heard it said, “Wow they eat the heck out of that Baleage”, let’s hope this is always true. Here is why:

Let’s say we want a 1300 lb cow to eat approximately 2%, of her body weight daily in DM that is:

1300 X .02 = 26 lbs DM daily from our lab report our dry hay was 82.7 % DM. Therefore, the cow would have to consume 26 lbs DM/ .827 (% DM in our hay) = 31.4 lbs of hay from our 2nd cut dry hay. If we substitute our baleage for the hay she would have to consume 31.4 DM from hay/ .33 (% DM of our baleage) = 95 lbs of baleage to receive the same amount of Dry Matter as provided in the hay. This is why dry matter content of feed is so important when calculating feed amounts, and value.

The above evaluation of dry matter need does not take into consideration rumen fiber fill. It should be noted that cattle DM intake is limited to a maximum of 1.5 % of their body weight in Neutral Detergent Fiber (NDF) for high quality forages. For a 1300 lb cow X .015 max NDF = 19.5 lbs of NDF is her max consumption. In our example our cow will need to consume 31.4 lbs DM X .618 % NDF content of the baleage = 19.4 lbs of NDF consumed, this is her limit. Forages with a greater than 60% NDF content on a Dry Matter basis may limit a cow’s ability to consume enough nutrients from the forage alone. If the forage quality is low they may need additional energy and protein.

Summarizing, forages can provide most of the major nutrients ruminant livestock need depending on their quality. What forages lack most frequently is energy. If energy levels being supplied in forages are marginal they will be inadequate in January and February when cattle deal with extreme cold. For example, at 10 degrees F and with wind chill, a cow’s energy requirement may increase by over 20 percent and will be further aggravated in wet muddy conditions. Forages will also lack in salt, and trace minerals, which can easily be provided with a loose free choice trace mineral. Vitamin A should also be provided during the winter months.The question is, how does your hay stack up? Do you expect your cattle to lose weight? If you had to compare the value of hay, doesn’t it make sense to evaluate forage nutrient content? The cost of poor body condition at calving can be expensive. The time to improve cattle body condition is during periods of low stress, not at calving, breeding season or January and February. Your local OSU Extension office can help you find a lab that can analyze forage. Utilize this valuable tool because the cost of not knowing forage quality is far too expensive.